In order to plan your language properly, you require a certain amount of time. You will, for example, need to determine what you are going to say (which message do you want to convey), how your story is built up and what your sentence structure should look like.
If you do not take enough time for this, you may soon experience all kinds of glitches in your speech. Because their language planning is not yet complete, cluttering speakers are struggling to determine what to say and how to do it. It is not surprising that cluttering speakers may often feel like their head is about to explode. For stuttering speakers this is exactly the other way round: they struggle to express what has already been planned in their head.
See the video down this page to learn more.